NOTE: The image must be uploaded into your Media Library to display. It cannot be hosted anywhere else. You need to re-upload the image from your computer via Media > Add New to and copy the new URL you'll get.

Image widgets require image URLs. Image URLs always end with the filetype extension (.jpg or .png etc). You didn't use an image URL, you used a shortlink, and a shortlink of a dashboard page at that. To use an image in an image widget, you upload the image via Media > Add New, and once it's uploaded you click Edit and copy the File URL you can see in the Save module: that's the URL you need to use. For an image you have already uploaded, you'll find the same thing if you go to Media > Library, hover over the image and click Edit.